During our investigation lath martensite was produced in low carbon steels by austenitization at 1200 °C/20 min, and the cooling of samples in ice water. The samples were tempered at a range of temperatures. The tempering effects on microstructure and on mechanical proprieties were investigated. Some samples with lath martensite microstructure were cold rolled and heat treated at different temperatures. Recrystallization was observed after heat treatment at 600-700 °C.